Thermoplastic resins exhibit excellent physical properties such as lower specific gravity, good moldability and impact resistance, as compared with glass or metal. Recently, with the trend of low cost and increasingly larger and lighter weight electronics, plastic products made of thermoplastic resins have been quickly replacing existing glass or metal based products, thereby broadening applications thereof to fields from electronics to automobile components.
In particular, recently, due to increasingly thinner electric and electronic products and change in design concept, there is an increasing need for transparent resins, which leads to increasing demand for functional transparent materials obtained by imparting functionalities such as scratch resistance and flame retardancy to existing transparent resins. In addition, development of resins having good scratch resistance is significantly demanded in the field of exterior materials.
In general, in order to improve scratch resistance of plastics, a hard coating method is widely employed in which organic-inorganic hybrid materials are doped into a surface of a final molded resin, followed by curing the surface using heat or ultraviolet irradiation, thereby improving scratch resistance of the resin surface. However, in such a hard coating method, an additional coating process is required, thereby causing a need for additional process time and cost increase as well as environmental problems. Accordingly, there is a need for non-painted resins exhibiting scratch resistance without hard coatings.
Meanwhile, systems in which flame retardants are added to polycarbonate resins have been employed as transparent flame retardant materials.
Polycarbonate resins are engineering plastics exhibiting not only excellent mechanical strength, flame retardancy, transparency and weather resistance but also good impact resistance, thermal stability, self extinguishability, dimensional stability and the like, and thus have been widely used in the production of electric and electronic products and automobile components. In addition, polycarbonates can replace glass in products such as lenses where both transparency and impact resistance are required. However, polycarbonates have a disadvantage in that they exhibit very poor scratch resistance. The flame retardant polycarbonate resins have scratch resistance in a pencil hardness level of about B—F, which is much less than a pencil hardness level of H˜3H required of scratch resistant resins.
Meanwhile, as existing transparent scratch resistant materials, mention can be made of acrylic resins represented by polymethyl methacrylate (PMMA). PMMA exhibits excellent scratch resistance in addition to good transparency, weather resistance and mechanical strength. However, PMMA exhibits poor impact resistance and flame retardancy. In order to supplement this, phosphorous flame retardants may be added to PMMA. However, it is difficult to obtain excellent flame retardancy, and physical properties such as heat resistance and impact strength can be reduced. Furthermore, there is no report up to now that flame retardancy is accomplished with the use of transparent acrylic resins alone.
As explained above, with the widespread use of resins as an exterior material of electric and electronic products, there has been increasing demand for transparent flame retardant and scratch resistant resins exhibiting transparency, scratch resistance and flame retardancy while maintaining good physical properties such as mechanical strength, heat resistance and the like. However, such products have yet to be made commercially available.